Bash tcp redirection end of transmission

I made a simple network service with xinetd which reads a string from tcp socket and outputs its encoded view. Original binary(qrencode) just reading stdin. It works fine when I use it with netcat as echo string | nc But it doesn't answer when I try to use it via bash tcp redirection. exec 7/dev/tcp// echo string >&7 cat <&7 It waits forever. I tried echoing \004, cat /dev/null to this fd and no luck. How can I make it working?